Heat pump apparatus and method



Dec. 21, 1965 G. T. NICKELL. ETAL 3,224,214

l HET PUMP APPARATUS AND METHOD Filed March '7, 1963 6 Sheecs-Sheecl 1 y@ OUTSIDE '1i-I AIR J INVENTORS @wsa/v fc4/fu BY S/i/wfz MGMSSJA.

Gw/ /f C/fff Dec. 21, 1965 G. T. NlcKr-:LL ETAL 3,224,214

y HEAT PUMP APPRATUS` AND METHOD Filed March 7, 1963 6 Sheets-Sheet 2 6:10AM im l miza L @D @94 fzwfi- Dec. 21, 1965 G. T. NICKELL ETAI. 3,224,214

HEAT PUMP APPARATUS AND METHOD Filed March '7, 1963 6 Sheets-Sheet 5 BY Gay H. c/fffk Dec. 21, 1965 G. T. NICKELL ETAI. 3,224,214

HEAT PUMP APPARATUS AND METHOD 6 Sheets-Sheet 4 Filed March 7, 1963 III. l 1| I v l l l l. III lll- MM 0K5, TCS w/i VWM N. Mm GSY GII/Y H. C/ffi/r www /9/"7" Dec. 21, 1965 G. T. NICKELL r-:TAL 3,224,214

HEAT PUMP APPARATUS AND METHOD Filed March 7, 1963 6 Sheets-Sheet 5 Dec. 21, 1965 Filed March 7, 19

HEAT PUMP APPARATUS AND METHOD 6 Sheets-Sheet 6 4- :I @arf/a5 74) l. 524 E78 8O E viz vf Arq OPE/Y SIG/VIL `0 vu ws l SEF V0 CLOS E 3ft? V0 SI5/VIL INVENTORS G07 C75/ffl United States Patent O 3,224,214 HEAT PUMP APPARATUS AND METHOD Grason T. Nickell and Samuel W. Glass, Jr., Greensboro,

and Guy H. Cheek, Charlotte, N.C., assignors to Air Conditioning Corporation, Greensboro, N .C., a corporation of North Carolina Filed Mar. 7, 1963, Ser. No. 263,667 30 Claims. (Cl. 62-81) This invention relates to a novel heat pump apparatus and to a novel process for its use.

In the operation of conventional heat pump units, provision must be made, at least during winter months when the evaporator unit of the heat pump system is in contact with cold outside air, for periodically defrosting the evaporator. Such defrosting is usually accomplished by directing heat to the evaporator coils to melt any ice which has formed.

One of the main disadvantages of heat pumps which are available on the market today is the fact that the heat which is used [for the defrosting step must be provided from the building or process which is being heated by the condenser of the heat pump system. For example, a conventional defrosting technique which is in fairly widespread use and which is illustrative of a system involving the extraction of heat from the building or process is one in which means are provided for reversal of refrigerant liow so that the evaporator normally in con tact with outside air is converted temporarily to a condenser and the heat given up by the condensing refrigerant is used to melt any ice which has formed on this unit. Quite obviously, such a system involves the conversion of what normally would be an indoor heating unit (viz., the condenser of the heat pump system) to a refrigerating element (viz., an evaporator) at least for the duration of the defrosting cycle, which will result in the extraction of heat from the building or process in or with which the heat pump system is being used.

In accordance with the .present invention, a novel heat pump system is provided which will not only perform a defrosting function without extracting heat from the building or process in connection with which the heat pump is being utilized, but which will do so without reversal of refrigerant flow and with minimum interruption of the normal temperature controlling functions of the heat pump system. The novel heat pump system of the present invention is also extremely significant in that it will simultaneously produce high temperature and low temperature fluid on a year-round basis independently of normal source temperatures.

It is accordingly a primary object of `the present invention to ,provide a novel heat pump system which is capable of being defrosted without reversal of refrigerant ow, without extracting heat for said defrosting from the space or uid being temperature controlled and with a minimum interruption of the temperature control function of said heat pump system.

It is another principal object of the present invention to provide a novel heat pump system which is capable of simultaneously producing high temperature and low temperature fluid on a year-round basis independent of normal source temperatures.

It is still a further important object of the present invention to provide a novel heat pump system which, utilizing many conventional elements, is capable of simultaneously producing high temperature and low temperature iluid on a year-round basis independent of normal source temperatures and which utilizes a novel outside combination evaporator-condenser unit on a non-reversing refrigerant ow arrangement not `only lfor augmenting the 3,224,214 Patented Dec. 2l, 1965 energy needs of the system but for performing a defrost function in a unique manner.

Itis a further significant object of the present invention to provide a novel combination heat exchanger (hereinafter to be referred to as a source-sink exchanger) which ICC t provides a dual function of bringing heat into a heat pump system when energy is required in the operation of the system and which serves to reject heat when the system contains more energy than is required, said source-sink exchanger also being useful as a defrost mechanism in an extremely eective manner.

It is another important object of the present invention to provide a novel temperature controlling process for performing a first function of. providing heat to a heat pump cycle to augment energy normally taken into a refrigeration cycle, to perform a second function of rejecting heat from a refrigeration cycle when too much energy is available to a heat pump system and to perform a third function of defrosting an evaporator element Without requiring reversal of refrigerant ilow in a heat pump system and requiring minimum interruption of the normal functions of the heat pump system.

It is still another important purpose of the present invention to provide a novel purge system in connection with the novel source-sink exchanger of the present invention to assure that the refrigerant in the heat pump system will always be in the active portion of the cycle and to minimize the required refrigerant charge and the possibility of refrigerant hammer during cycle changes.

These and other significant advantages of the present invention will become more apparent in connection with the ensuing description, appended claims, and drawings wherein:

FIG. 1 represents a schematic diagram setting forth the various elements involved in the novel heat pump system of the present invention and the relationship of such elements to one another;

FIG. 2 is a top plan view of a compact unit adapted to contain the novel heat pump system of the present invention and illustrating the arrangement of the sourcesink exchanger to blowers associated with said exchanger;

FIG. 3 is a sectional View taken along lines 3--3 in FIG. 2;

FIG. 4 is a left elevation of the structure shown in FIG. 7, partly broken away;

FIG. 4a is a right elevation of the structure shown in FIG. 7, partly broken away;

FIG. 5 illustrates the relative arrangement of the evaporator and condenser tubes in the source-sink exchanger;

FIG. 6 is a greatly enlarged sectional view taken along lines 6-6 of FIG. 5;

FIG. 7 is a front elevation, partly broken away, of the novel source-sink exchanger `of the present invention;

FIG. 8 is a left elevation of the structure shown in FIG. 7 showing in full lines the evaporator circuiting of the source-sink exchanger and in dotted lines a portion of the condenser 4circuiting of said exchanger;

FIG. 9 sets forth a right elevation of the structure of FIG. 7 illustrating in heavy lines the evaporator circuiting of the source-sink exchanger and in dotted lines a portion of the condenser circuiting;

FIG. 10 is a left elevation of the structure of FIG. 7 `showing in heavy lines the condenser circuiting of the source-sink exchanger and in dotted lines a portion of the evaporator circuiting;

FIG. 1l illustrates a partially broken away top plan view of the structure of FIG. l0 showing only the condenser circuiting of the source-sink exchanger;

FIG. l2 illustrates a right elevation of the structure of FIG. 7 showing in full lines the condenser circuiting of the source-sink exchanger and in dotted lines a portion of the evaporator circuiting;

FIG. 13 is a partially broken away top plan view of the structure shown in FIG. 12 but illustrating only the condenser circuiting of the source-sink unit;

FIG. 14 is a partial schematic of a modified form of the heat pump system of the present invention; and

FIGS. 15a-15n, inclusive, are block diagrams illustrating the automatic sequencing means adapted for automatic operation of the novel heat pump system of the present invention.

A general understanding of the broad inventive aspects of the novel heat pump system and process of the present invention may best be understood through reference to the schematic flow diagram set forth in FIGURE 1. As illustrated therein, the high pressure side of a compressor is connected by means of a refrigerant flow conduit 22 to a condenser 24. rThe closed heat pump circuit continues through refrigerant flow conduit 26, a supplemental condenser 28, conduits 30 and 32, valve 34, conduit 36, receiver-accumulator 38, conduits `40 and 42, valve 44, expansion valve 46, evaporator 48, conduit 50, back-pressure valve 52, conduits 54 and 56 and back into the low pressure side of compressor 20. As will be noted receiveraccumulator 38 also communicates with conduit 56 through conduit 51, valve 53, and conduit 55 for a venting purpose to be described more specifically below.

In accordance with the present invention, refrigerant flow conduit 30 is connected in flow relation to a conduit 58 which, in turn, communicates with a conduit 60 through a valve 62. For a reason to be explained later, a pressure relieving valve 64 (designated by the symbol PRV) is positioned in a by-pass 66 about valve 62.

As is shown more specifically in FIGURES 4-13, refrigerant flow conduit 60 is in fiuid flow relationship to a header 68 which, as will be described in greater detail below, is in fluid flow relationship with the condenser portion of the source-sink exchange unit indicated generally at 70. The condenser tubes of the source-sink exchanger 70 in turn are in fluid flow communication with a header 72 which, in turn, is connected in flow relationship to a conduit 74. As will be seen by reference again to FIGURE 1, conduit 74 communicates with conduit 36 and, through the latter, to receiveraccumulator 38, which serves as a refrigerant reservoir and superfluous flow accumulator. Receiver-.accumulator y38, in turn, communicates through conduit 40 with the main closed circuit described previously.

As was previously described in connection with the -basic heat pump circuit, a refrigerant flow conduit 40 communicates from the receiver-accumulator 38 with la conduit 42 which leads ultimately vto expansion valve 46 and evaporator 48. As will be noted in FIGURE 1, an alternate path for refrigerant flowing through conduit 40 is through conduit 76, a valve 78, an expansion valve 80, a conduit S2 and, from the latter, into the evaporator tubes of the source-sink exchanger 70, as may be seen more particularly in FIGURES 4-13.

As shown in FIGURES 4-13 (as indicated by the four arrows leading from refrigerant ow conduit 82 in FIG- URE 1), refrigerant flowing through conduit 82 is divided into four portions one of which passes into each of four evaporator distributors, S4, 86, 88 and 90 (see FIGURES 7 and 8), although the conduit connections between conduit 82 and distributors 84, 86, 88 and 90 have not been shown for purposes of clarity of illustration. As shown more particularly in FIGURES 7 and 8, each of the distributors 84, 86, 88 and 90 contains a plurality of distributing conduits 92 each of which communicates in fluid flow relationship with the inlet of one horizontal evaporator coil 94 which will be described in greater detail below. (While only a portion of such distributing conduits 92 have been shown in full lines `and the remainder in broken lines for clarity of illustration, it is to be understood that each of said distributors 84, 86, 88 and 90 will have one distributing conduit 92 for each vertically spaced evaporator coil 94 in the vertical quarter 0f the source-sink ex- Cil changer 70 with which it is associated.) The outlets of evaporator coils 94 all communicate with headers 96, 98, and 102 which, in turn, communicate in fluid flow relationship with conduit 56 (see FIGURE 1), although the connections between headers 96, 98, 100 and 102 with conduit 56 have not been shown for purposes of clarity of illustration. As will be seen in FIGURE 1, conduit 56 communicates in fluid flow relationship with the low pressure side of compressor 20.

As previously indicated, details of the structure of the source-sink exchanger 70 are illustrated in FIGURES 4- 13. In advance of further discussion `as to such details, however, brief mentioned should be made of the nature of the views set forth in FIGURES 4-l3. As indicated in the description of the drawings previously set forth, FIGURES 8 and 10 set forth left elevational views of the structure of FIGURE 7 and FIGURES 9 and l2 set forth right elevational views of said structure. In actuality, both of FIGURES 8 and l0 are simplified versions of the same left elevational view of the structure of FIGURE 7, FIG- URES 9 and 12 correspondingly being simplified versions of the same right elevational view of the structure of FIG- URE 7. Such structures have been simplified primarily for purposes of illustration, FIGURES 8 and 9 illustrating in full lines solely the evaporator circuit and FIGURES 10 and 12 setting forth in full lines solely the condenser circuit, the dotted lines in each drawing representing a portion of the other of the condenser or evaporator circuits as the case might be. A composite picture of the left elevational views of FIGURES 8 and 10 is actually shown in FIGURE 4 and a composite of the right elevational views of FIGURES 9 and 13 is shown in FIGURE 4a, both however being partial views merely for purposes of illustration.

The preferred embodiment of the source-sink exchanger 70 comprises an independent outdoor evaporator section and an independent outdoor condenser section, such sections each consisting of a plurality of vertically spaced tubes, the tubes of the evaporator section alternating in a vertical direction with those of the condenser section and being in staggered relation to one another along vertical planes. This arrangement may be clearly seen in FIGURES 4, 4a, 5, 6 and 8-13. As shown therein, hot uncondensed refrigerant gas passes from conduit 60 into condenser header 68 and thence into the vertically spaced condenser tubes 106, from which condensed refrigerant is discharged into header 72 and back into the system through conduit 74. Sandwiched vertically in between successive condenser tubes 106 are a plurality of alternating evaporator tubes 94 which, as may be seen most clearly in FIGURES 4 and 4a, communicate on their inlet side through one of the distributing conduits 92 with one of the distributors 84, 86, 88 or 90 (depending upon the vertical level in the source-sink exchanger 70) and thence through conduit 82 with expansion valve 80. On their discharge end, such evaporator tubes 94 communicate with one of the headers 96, 98, 100 or 102 (depending upon the vertical level in the source-sink exchanger 70) and thence with the main body of the system through conduit 56.

While the source-sink exchanger 70 is thus preferably divided up into two separate circuits, one for use as a heat rejection condenser and the other as a heat source evaporator, the source-sink exchanger 70 is desirably a single unit with the tubes of the condenser and evaporator portions being in heat exchange relationship with one another by means of a plurality of spaced platetype fins 108 which, as shown more particularly in FIGURE 7, are arranged vertically through the entire depth and extent of the source-sink exchanger 70. The resulting arrangement of alternating vertical levels of evaporator and condenser tubes which pass through the vertical plate-type fins 108 is well illustrated in FIGURES 5 and 6.

For a purpose to be described more particularly below, a purge conduit 110 connects refrigerant flow conduit 74 through a valve 112 with expansion valve 80.

[Note: Conduits 74 and 56 have been positioned in FIGURE l differently than as shown in FIGURES 7 13 merely for clarity of illustration] As best illustrated in FIGURES 2-4, the entire heat pump system of the present invention is adapted to be compacted into a packaged unit which may contain all the essential elements of the system. As shown in these figures, source-sink exchanger 70 is adapted to be located in a portion of the packaged unit in contact with the outside air, such air to be drawn into a cornpartment 114 by a plurality of :blowers 116 (which may be of the conventional squirrel cage variety), such blowers ultimately forcing the air out of the neck 118 of the blower either into the outside atmosphere or to a point of use as Will be more particularly described hereinafter. Blowers 116 are provided (as `shown in FIG- URE 3) with a plurality of dampers 120 in their necks 118 for a purpose to be described below. The compartment 122 of the packaged heat pump unit may suitably contain the remaining elements of the system, including, for example, the compressor 20, the condensers 24 and 28, the receiver-accumulator 38, the evaporator 48, and the associated pumps, valves, refrigerant flow conduits, etc., required to complete the entire system.

As best shown in FIGURE l, a high temperature iiuid supply system indicated generally at 124 is in heat exchange association with condenser 24 and a low temperature fluid supply system indicated generally at 126 is in heat exchange relationship with evaporator 48.

The high temperature fluid supply circuit 124 comprises a conduit 128 leading from condenser 24, a supplementa-ry heating unit 130, conduit 132, air separation tank 134, conduit 136 and circulation pump 138 from which high temperature uid 139 is supplied to a point of use. A return conduit 140 is provided from said point of use back into said condenser 24, conduits 140 and 128 being in fluid flow communication in a conventional manner (not shown).

Low temperature iiuid supply circuit 126 comprises a conduit 142 leading from evaporator 48, defrost stage supplementary heatingmunit 144, conduit 146, an air separation and expansion tank 148, conduit 150, and a recirculation pump 152. Pump 152 can be rendered operative to pump low temperature fluid through conduit 154, through evaporator 48 and back up through conduit 142 or, when pump 156 is operative, low temperature fluid can pass from pump 152, through conduit 158 and, by means of pump 156, to a point of use of the low temperature fluid supply. A return conduit 160 is provided from said point of use back into conduit 154 and into the low temperature fluid supply circuit.

As shown in FIGURE 1, uid (which may conveniently be city water) may be provided both to the high temperature fluid supply system 124 and the low ternperature fluid supply system 126 from conduit 162 and into either air separation tank 134 or air separation and expansion tank 148 by means of conduits 164 and 166, respectively.

In the following paragraphs, a typical method of operation of the above-described heat pump system will be set forth in connection with one of the primary anticipated .uses of such system, viz., for commercial and industrial building air conditioning accomplished by hot and cold water in two different circuits.

Generally speaking, the heat pump system of the present invention may be employed in three different cycles of operation, the rst of which will be referred to hereinafter as the standard cycle, the second of which will be described as the energy source cycle and the third as the defrost cycle. In the standard cycle of operation, which will most often be employed in warmer weather, the system contains more energy than is needed by the various demands on the system and, accordingly, the

system is operated so that there will be a net energy rejection (in the form of heat) from the system through the agency of the sink portion of the source-sink exchanger. The energy source cycle will come into operation when the system requires additional energy for normal requirements, which will most often take place in colder weather. In the operation of this cycle, there is a lnet energy transfer to the system from outside the system by means of the source-sink exchanger. Lastly, the defrost cycle is utilized to defrost the evaporator coils in the source-sink exchanger, which defrosting will be required from time to time during the operation of the system under sufficiently cold weather conditions.

In the operation of the standard cycle, hot refrigerant gas is discharged from the compressor and is partially condensed in condenser 24 and, if an additional high temperature exchanger is provided (such as is shown in broken lines in FIGURE l), additionally in condenser 28. High temperature fluid pump 138 is operative to circulate fluid in heat exchange relationship to condenser 24 so as to heat up such fluid and deliver it to a point of use as required. Valve 62 istopen while valve 34 is closed so that the partially condensed refrigerant will iiow through conduit 60 and into the condenser portion of the source-sink exchanger 70, wherein the remaining portion of the refrigerant gas is completely condensed. The condensed refrigerant liquid will leave the condenser circuit through conduit 74, will pass into receiver-accumulator 38, through conduits 40 and 42, valve 44 and through expansion valve 46, following which evaporation will take place in evaporator 48. The evaporated refrigerant Will then pass into conduit 50, back pressure valve 52, conduits 54 and 56, and back into the low pressure side of compressor 20.

Since both pumps 152 and 156 will be operative during this cycle, fluid circulating between conduits 142 and 154 and through evaporator 48 will be cooled by evaporation of the refrigerant and low temperature uid will be supplied to a point of use through pump 156, that portion of such low temperature uid which is not used returning to the system through conduit 160,

During the operation of this standard cycle, valves 78 and 112 are closed and valve 53 is open throughout the operation of the compressor 20, to serve as a small vent line from receiveraccumulator 38. In addition, back pressure valve 52 is wide open and since blowers 116 are operative to draw outside air across the source-sink exchanger condenser coils 106, there will be a net energy loss from the system to the outside air resulting from condensation of refrigerant in the condenser coils 106.

During the operation of the energy source cycle, the pressure relief valve 64 and valve 62 are closed. Hot gas is discharged from the compressor 20 and is completely condensed in condenser 24 (or, if a condenser 28 is also present, in both of condensers 24 and 28). Pressure relief valve 64 will become operative to by-pass valve 62 whenever excessively high refrigerant pressures exist in condensers 24 and, if used, 28. The high temperature fluid supply circuit 124 is operative as in the standard cycle, which will provide a source of high temperature fluid to the point of use. Valve 34 is open, permitting the condensed refrigerant liquid to pass from conduit 30, through conduits 32 and 36 and into receiver-accumulator.38.

From receiver-accumulator 38 condensed refrigerant flows in one or both of two directions, depending upon the needs of the system. When it is not desired to make up any energy deficiency in the system, valves 78 and 112 can conveniently be closed and condensed refrigerant uid passed only through conduit 42, valve 44, expansion valve 46, evaporator 48, back pressure valve 52, conduit 54, conduit 56 and back into the system through compressor 2t). When a net energy gain to the system is required, at least a portion (or all, depending upon the needs of the system) of the condensed refrigerant will pass into conduit 76, through valve 78, through expansion valve 8G and conduit 82 and into distributors 84, 86, 88 and 90 of the evaporator portion of the source-sink exchanger 7i). Since blowers 116 will be operative at this time to draw outside air across the source-sink exchanger evaporator coils 94, there will be a net energy gain to the evaporated refrigerant in said evaporator, coils 94 and such energy gain will be carried along in the form of a higher refrigerant energy level (gas) out of the source-sink exchanger 70, through conduit 56 and back through compressor 20. Quit obviously, where lesser energy gains are required, a portion of the condensed refrigerant from receiver-accumulator 3S can be .passed through conduit 76, etc., into the source-sink evaporator section and another portion into evaporator 48 through the appropriate passages.

During the operation of the energy source cycle, valve 53 is operative to serve as a small vent line Whenever the compressor is operating and valve 112 will be open to permit purging of the sink (condenser) portion of the sourcesink exchanger '70 so as to assure that the refrigerant will be in the active portion of the cycle, to minimize the required refrigerant charge and the possibility of refrigerant hammer during the cycle change. Such purged refrigerant is passed into the source portion of the source-sink exchanger 70 through a side port of expansion valve 80. During this cycle, the back pressure valve 52 is controlled to maintain the refrigerant suction level required for the particular temperature desired in evaporator 48. In addition, it is to be noted that whenever a portion of the condensed refrigerant is passed into evaporator 48 during this this cycle, the low temperature fluid supply system is operative as in the case of the standard cycle.

The defrosting cycle has two stages, the first stage being a heat storage stage and the second being the actual defrosting stage.

In the first stage of the defrost cycle, the low temperature fluid supply pump 156 is inoperative, the recirculating low temperature fluid pump 152 is operative to cause fluid flow through evaporator 48, supplementary heating unit 144 and the associated components in the recirculation circuit 126 for the low temperature fluid, the supplementary heating unit 130 in the high temperature fluid circuit 124 is turned off to limit external energy demand and the supplementary heating unit 144 in the low temperature fluid recirculation circuit 126 is active to store energy for the second stage in the defrost cycle. Otherwise, the system is operated during the first stage as in the energy source cycle but with valve 44 closed so that all of the condensed refrigerant from receiver-accumulator 38 will pass into the source portion of the source-sink exchanger 70 and will by-pass evaporator 48 by passing back to compressor through conduit 56.

Operation of the system in this manner is continued until the low temperature fluid being recirculated by means of pump 152 has reached a sufficient temperature level, which normally will take place after about three minutes of operation in this stage. This temperature level will necessarily vary depending upon the size of the components used and other such factors, but in general will be in the order of about 60 F. At this point, the high temperature fluid circulation pump 138 is turned olf, blowers 116 rendered inoperative and the blower dampers 120 closed, circulation of high temperature fluid through high temperature circuit 124 interrupted by turning off pump 138, and the system otherwise converted back to operation under the standard cycle, with valve 44- now open, though the now heated low temperature fluid in circuit 126 is still recirculated and heated as in the first stage of the defrost cycle by continuing to maintain pump 156 in an inoperative condition. In this second stage of the defrost cycle (which usually lasts about one minute), the compressor 20 is caused to operate at full capacity, picking up heat from refrigerant leaving the evaporator 48 and passing it into condenser 24. By stopping the circulation of high temperature fluid through the high ternperature fluid circuit 124 during this stage, condenser 24 will have little effect on the high pressure refrigerant vapor and such vapor will pass on through conduits 30 and 68 and into the sink portion of the source-sink exchanger 70. Since the source and sink portions of the source-sink exchanger '70 have common heat exchanger surfaces (the plate fins 108), the condensation of the refrigerant gas in the sink portion will quickly result in the defrosting of the sourcesink exchanger 70. By equipping the source-sink exchanger 70 with a suitably placed temperature sensing element (not shown), the completion of the defrosting operation will be readily noted when the exchanger coils have reached a suitably high temperature to assure the completion of the defrosting operation (i.e., about 45 F.) and, by use of conventional automatic control mechanisms, the system can be converted back either to the standard or energy source cycles for normal operation as desired.

Thus, as will be seen from the above description, low temperature fluid recirculation pump 152 is operative whenever compressor 2f) is operating, the point of use low temperature fluid pump 156 operates at all times except during the entire defrost cycle, and the high temperature fluid pump 138 is operative to provide high temperature fluid to the point of use at all times except during the last stage of the defrost cycle. Since, as will be pointed out in more detail below, the defrost cycle will be used no more frequently than `once per minutes and since the need for the defrost operation will ordinarily exist only during colder weather with low temperature fluid needs being lower at such time, the interruption of the low temperature fluid flow to the point of use during the defrost cycle will not be significant. Similarly insignificant will be the minimal interruption of the high temperature fluid :supply to the point of the use. The significance of the latter is that by means of the present system, hot water will be generated substantially completely continuously whenever the system is operating, thereby providing a means for intermediate season heating, heating for dehumidification purposes, reheat for control uses, etc.

Quite obviously, the defrost cycle may be omitted where source temperatures are sufficiently high to prevent freezing of the source portion of the exchanger 7 0.

Generally speaking, no defrosting problem will arise in connection with the evaporator 48. This problem is avoided in at least two respects in the system of the present invention, first by providing continuous recirculation of low temperature fluid between low temperature fluid circuit 126 and evaporator 48 whenever compressor 20 is operating (as previously described) and secondly by means of back pressure valve 52. The latter is operative during the lenergy source cycle to maintain a sufliciently high suction pressure on the refrigerant in evaporator 48 to prevent the low temperature fluid (i.e., water) from freezing. In the case of the use of evaporator 48 in a process environment where the low temperature fluid is not water, the back pressure regulator will maintain the suction condition within evaporator 48 above the level desirable with such fluid. If one is not concerned with a freezing problem in evaporator 48, back pressure valve 52 may be omitted entirely.

As a specific example of the operation of the heat pump system of the present invention, the use of the system for producing hot and chilled water for a Conventional building heating and cooling system may be considered. A typical hot water design temperature is F., with chilled water being generally supplied at 45 F. During the summer and intermediate seasons, the heat pump will generally be operated in the standard cycle. So long as there is a net heat gain to the building, the system will continue to operate in the standard cycle and there should be sullicient hot water at a suitably high temperature to satisfy the heating requirements. Under most conditions in the course of the standard cycle, some condensing would take place in condenser 24, some additional condensing in 9. a domestic hot Water pre-heater unit as hot water is used within the building (this additional unit being represented, for example, by unit 28 in FIGURE 1) Iand the remaining condensing in the outdoor sink portion of the source- `sink exchanger 70.

During cold weather, the temperature .of the hot water leaving the condenser 24 will decrease. When this temperature drops to approximately 105 F., the system is switched to the heating or energy source cycle. When in this cycle, heat will be picked up by the system through the source portion of the source-sink exchanger 70 and such heat will be ultimately delivered to the hot water heating condenser 24. Such hot water will ultimately increase in temperature and, when it reaches approximately 112 F., the system will be switched back to the standard cycle.

Under normal conditions, the heat pump system of the present invention will be required to defrost after it has been in the heating cycle for a given time. Since the system will, as described below, be completely automatic, the system will be provided with a timing mechanism which, approximately every 90 minutes, will close a circuit which will give the system .an opportunity (approximately seconds) to enter the defrost cycle if the therm-ostat on the source-sink exchanger 70 indicates the presence of frost. If frost conditions exist, automatic controls in the system will automatically place the system in the defrost cycle; otherwise, the system will continue operating as it had been.

As previously indicated, during the defrost cycle pump 152 in the low temperature fluid supply circuit 126 continues to operate to recirculate such fluid through evaporator 48 while the point of use pump 156 is rendered inoperative. Since the heater 144 is operative to heat such low temperature liuid in the course of its recirculation, such uid will ultimately increase in temperature and, when it reaches approximately 60 F., the second stage of the defrost cycle will .automatically commence and the source portion of the source-sink exchanger 70 will be defrosted.

During the second stage of the defrost cycle, as previously indicated, dampers 120 of the Iblowers 116 are closed, the blowers rendered inoperative and hot water pump 138 is inoperative. Otherwise, the system will operate effectively under the standard cycle, absorbing heat from the low temperature fluid recirculation circuit 126 and delivering such heat to the sink portion of source-sink exchanger 70. Upon a rise in temperature of the refrigerant liquid in the sink portion (as sensed by the thermostat on the source-sink exchanger 70) to approximately 45 F., the system is taken out of the second stage of the defrost cycle and returned either to the standard or energy source cycles, depending upon the hot and chilled water requirements of the building in which the system is being employed.

It is to be understood, of course, that regardless of which cycle is employed in the process of the present invention, the refrigerant flow sequencing is carried out in accordance with well understood principles of energy transfer and refrigeration so as to insure a complete energy balance among all energy transfer components of the system for maximum operating efiiciency.

It will be recalled that FIGURE 1 illustrates the presence (in broken lines) of a supplementary high temperature exchanger 28. This additional unit may be provided as a supplementary condenser, for use as a domestic hot water pre-heater or process fluid heater for example, if required. While not so illustrated in FIGURE l, such supplementary exchanger 28 will be provided with a high temperature iluid circuit similar to that designated generally at 124.

During the standard cycle, condenser 24 could condense the full capacity of the system or any amount down to zero, depending upon the use requirements of the high temperature fluid. Under most conditions, condenser Z4 would not do all of the condensing, at least a portion of the condensing normally taking place in supplementary condenser 28 in proportion to the use requirement. The sink portion of source-sink exchanger 70, on the other hand, will either augment the condensing function of condensers 24 and 28 or, if desired, it could handle the entire condensing requirement. Thus, supplementary exchanger 28 provides a means in addition to the sink portion of exchanger 70 to remove energy from the system when a net energy rejection is called for while utilizing such energy by providing a secondary source of high temperature fluid. This excess heat could be made available, for example, to preheat domestic hot water.

As previously indicated the source-sink exchanger 70 in the preferred embodiment contains separate evaporator (source) and condenser (sink) circuits which are rendered operative alternatively but not simultaneously. This arrangement, in combination with the common plate fins 108 which both share, is an important aspect of the present invention since it provides added heat exchange capacity to the active section of the source-sink exchanger 70 and, as a result, performs a vital function in the defrost cycle. This arrangement also makes possible the defrost operagon without the necessity for reversal of refrigerant iiuid As will be apparent, however, modiiications may be made in the details of the source-sink exchanger 70 while adhering to the broad inventive concept disclosed above. For example, the circuiting and staggered arrangement of the source and sink portion tubes could change depending on the size of the unit employed, and the overall size, total number of rows, size of tubes and of tins, etc., could be as well modified, through especially advantageous results are obtained with the specific structure heretofore described in detail. Merely by way of example, instead of the arrangement shown above, arrangements of the elements of exchanger 70 may include horizontal coilhorizontal tube; vertical tube-vertical coil; angular oblique or obtuse arrangement; etc. As another example, conduit connections between the condenser and evaporator coils of exchanger 70 could be modiied to change the relationship between refrigerant Iiow and air ilow or between refrigerant iiow in the condenser portion with respect to refrigerant flow in the evaporator portion of said exchanger. (The latter is particularly significant in the arrangement of FIGURE 14.) As an example of such flow modification, conduit connections could be modied so that instead of hot gas flow in a general direction opposed to air iiow (as in the case in FIGURE 5), hot gas flow could be in the opposite direction. Such conduit modifications would not, of course, take place during the operation of the system but are merely suggested as alternative structural arrangements.

If desired, in addition, important advantages may be nevertheless retained by modifying the refrigerant flow relationship between the sink and source portions of exchanger 70 as shown in FIGURE 14. In the modiiied version of the present heat pump system shown in that ligure, the system is otherwise identical to that shown in FIGURE 1 except for the refrigerant ow circuiting between supplementary condenser 28 and source-sink exchanger on the one hand and the source-sink exchanger and receiver-accumulator 38 on the other.

As illustrated therein, supplementary condenser Z8 is connected directly to exchanger 70 through conduit 130 without the intermediary of valves 62 and 64, conduit 130 actually feeding into header 68 on exchanger 70 as did conduit 60 in FIGURES 1 and 10. Refrigerant ilow from the sink portion of exchanger 70 leaves through conduit 74 as before but directly into receiver-accumulator 38 without rst -passing through a check valve as in FIGURE 1. The remaining portion of the circuit of FIG- URE 1 has been left intact, except that purge conduit 110 and its associated valve 112 have been eliminated.

Except for a slight modification of the lenergy source cycle and the first stage of the defrost cycle, the operation of this system is otherwise identical to that of the system of FIGURE 1. In the energy source cycle, instead of bypassing the sink portion of exchanger 70 (which was effected by closing valves 62 and 64 and opening valve 34), refrigerant which has been fully condensed in condensers 24 and/or 28 is passed through conduit 130, through the sink portion of exchanger '70 (which, while it serves to pre-cool the refrigerant prior to its entry into the source portion of exchanger 70, performs no condensing function), out of the latter through conduit 74 and into receiver-accumulator 38, and into the source portion of exchanger 70 as desired (as in the case of the energy source cycle of the system of FIGURE l). Since the refrigerant must pass through the sink portion prior to its entry into the source portion, the necessity for purge conduit 110 and valve 112 has been obviated.

In the first stage of the defrost cycle, the same modification in the operation of the corresponding stage of the system of FIGURE 1 is made as is described above, that is the refrigerant must physically pass through the sink portion of exchanger 70 before it reaches the source portion.

Thus, the main aspect of the above modification is to use the sink portion of exchanger 70 as a refrigerant iiow conduit when the source portion is in use, though it will be understood that the former will not act as a condenser in such capacity unless the sink portion is actually desired to be used as such.

Several advantages accrue from the modification described above and illustrated in FIGURE 14. In the first place, such modification obviates the necessity for at least five valves and associated conduit material and simplifies controls for the system. Secondly, this modification also serves to increase the operating eiciency of the system in that energy present in the refrigerant as it passes through the sink portion of exchanger 70 during the energy source and defrost cycles will be transmitted in the form of heat both to the outside air passing over the coils of exchanger 70 and to the refrigerant iiowing through the source portion of exchanger 70. This will elevate the source level and provide improved cycle efiiciency.

As will be apparent, while the novel heat pump system of the present invention may be operated manually if desired, the system may be rendered completely automatic by means of suitable electric circuitry and automatically operating solenoid valves, temperature and pressure sensing elements, etc. For example, in the preferred arrangement, a suitable temperature sensing element will be positioned in the high temperature fluid circuit 124 so as to position the entire system in the energy source cycle whenever the temperature of the high temperature fiuid drops below a desirable minimum. During periods of great demand for external energy, such temperature sensing element will also render operative the supplementary heater 130 in the high temperature fluid circuit 124 and will render such heater inoperative when such demand ceases. A temperature sensing element placed in the low temperature fluid recirculation circuit; 126, i.e., in conduit 142 or 154, will be operative to control valve 44 to permit the maintenance of the low temperature fluid at a desirably low level. The latter will be accomplished by permitting greater iiow through valve 44 when the temperature of the low temperature fluid is not low enough and a lesser (or no) flow through valve 44 when such temperature is low enough. A refrigerant pressure sensing element will also be provided in the high (condensing) side of the refrigeration circuit (i.e., in conduit 42 just upstream of valve 44 or in conduit 22 just upstream of condenser 24) to limit the capacity of the sink (condenser) portion of source-sink exchanger 70 as the need arises. This pressure control, which is operative only during the standard cycle, functions automatically to modulate dampers 120 in blowers 116 (FIGURE 3) and to render inoperative blowers 116 in response to pressures below a predetermined level, the effect of the operation of this control being to maintain a suitably high head pressure to cause ow through the expansion elements. A pressure device sensitive to the pressure in the low (suction) side of the system, operative only during the standard cycle, will function to reduce the capacity of the compressor dependent upon requirements of the evaporator 48. This device is an integral part of the compressor 20. As the suction pressure drops, this device automatically reduces the number of operable cylinders, thereby reducing the capacity of the compressor. An over-riding device, in the form of an electro-pneumatic relay, is also provided to over-ride this last mentioned device to cause compressor 20 to operate fully loaded during the energy source and defrost cycles. An automatically controlled drain valve will be provided to purge the sink portion of exchanger through conduit and valve 112 when the system is switched from the standard cycle to the energy source cycle. The temperature sensing element which will convert the operation of the system to the defrost cycle will be located on a metal surface on the air entering side of the source-sink exchanger 70.

In order to illustrate more clearly the automatic operation of the novel heat pump system of the present invention, electronic circuits for automatic control of the system have been set forth in block diagram in FIGS. 15a-1511, inclusive. These block diagrams, which set forth only the essential mechanisms and operations for automatic control of the aforedescribed system, will be discussed in the following paragraphs with reference to the system illustrated in FIGURES l-13.

In FIG. 15a, automatic electronic controls are set forth to illustrate the conversion of the heat pump system from the energy source cycle to the standard cycle, and vice-versa. As shown therein, a thermostat in high temperature fluid circuit 124 (i.e., in conduit 128) emits an output signal which may set either a detector 200 or a detector 202. When the output signal from the thermostat in circuit 124 (hereinafter referred to as T124) indicates that the temperature in circuit 124 has fallen below a predetermined point, it sets detector 200 and detector 200 will remain set until it is reset by the output signal from detector 202. Detector 202 will, in turn, be set when the output signal from T124 indicates a temperature in circuit 124 which has risen above a predetermined point, which will result in the resetting of detector 200. Thus, one of detectors 200 and 202 will be producing an output signal at all times during the operation of the heat pump system. As will be seen in FIG. 15a, the output signal from detector 200 will pass through a normally enabled gate 204. A signal passing through the gate 204 is designated in FIGS. 15a-1511 as E-S and, as will be described in greater detail below, transforms the heat pump system into operation under the energy source cycle. On the other hand, the output signal from detector 202 passes through the normally enabled gate 206. A signal passing through the gate 206 is designated S and transforms the system into operation under the standard cycle. As will be apparent, because of the resetting of one of the detectors 200 and 202 by the production of an output signal from the other, the operation of the energy source and standard cycles are mutually exclusive, one being rendered inoperative when the other is operative.

The signal identified in FIG. 15a by the letter D, as described in greater detail below, is emitted throughout both stages of the defrost cycle and will, whenever it is produced, inhibit gates 204 and 206 so as to render inoperative both the energy source and standard cycles during the defrost cycle.

Reference to the various ones `of FIGS. 15a-1511, inclusive, will serve to illustrate the operation of the system depending upon whether signal E-S or signal S is emitted. As may be seen in FIG. 15C, signal S is passed through the OR gate 208 and is applied to the O input of a valve 13 operator 210. Valve operator 210 upon receiving such signal at its O input will -open valve 62. FIG. 15d illustrates that signal S will be passed through an OR gate 212 and applied to the C input of valve operator 214, which will in response thereto close valve 34. An S signal will also be passed through OR gate 216 into the C input of valve operator 218 (see FIG. 15e) to close valve 112. FIG. 15g shows that signal S will also be applied to an open signal generator 220 the signal from which will pass through OR gate 222 and be applied to valve positioning servo 224, causing it to open back pressure'valve 52. As shown in FIG. 15h, signal S will pass through an OR gate 226 and be applied to a close signal generator 228 which, in turn, will generate a signal through OR gate 230 to induce valve positioning servo 232 to close valve 78. Finally, as shown in FIG. 15n, signal S will enable gate 234 to pass the signal generated by pressure transducer 236 (which may conveniently be located in conduit 22) both for the purpose of modulating dampers 120 and for shuttting off blowers 116 when the pressure in the system drops below a predetermined point, thus permitting pressure transducer 236 to serve as a head pressure controlling device. More specifically, the signal from pressure transducer 236 passing through gate 234 during the standard cycle will pass through OR gate 238 and will be applied to a positioning serzo 240 which will, in turn, modulate the position of dampers 120 in accordance with the pressure in the system as indicated by the signal from pressure transducer 236. The lower the pressure the more the dampers 120 will be closed. Simultaneously, when the signal from pressure transducer 236 indicates that the pressure drops below a certain predetermined level, the detector 242 in response to such signal will set and will generate a signal which will pass through OR gate 244 and turn off blowers 116. The detector 242 will remain set and maintain blowers 116 in an inoperative condition until such time as the pressure rises above said predetermined level.

As shown in FIG. 15C, signal E-S will pass through OR gate 246 and be applied to the C input of valve operator "210, which will then close valve 62.

At the same time, signal E-S will pass through OR gate 248 (see FIG. 15d) and be applied to the O input of valve operator 214 which `will in turn open valve 34. Signal E-S will also pass through OR gate 250 to be applied to the O input of valve operator 218, which will open valve 112 (see FIG. 15e). As shown in FIG. 15g, signal E-S will pass through OR gate 252 and Will enable gate 254. An output signal which is proportional to the pressure in conduit 50 is generated by pressure transducer 256 and applied to the gate 254. When gate 254 is enabled, the output signal of the pressure transducer 256 will pass through gate 254 and OR gate 222 and be applied to valve positioning servo 224, which will vary the opening of back pressure valve 52 in accordance with the signal produced by pressure transducer 256. The valve positioning servo 224 responds to the signal from the pressure transducer 256 to move the valve 52 towards closure in response to a decrease in .pressure and to open the valve 52 in response to an increase in pressure in conduit 50. As will be seen in FIG. 15g, the valve positioning servo 224 will operate under this variable control only when a signal is produced as described above during the energy source cycle or, as

`will be described in greater detail below, during the rst 14 the intensity of such pressure, the output signal from pressure transducer 262 will be greater or less and, Whenever gate 260 is enabled as set `forth above, such output signal will pass through gate 260, through OR gate 230 and will be applied to valve positioning servo 232, which will in turn vary the opening in conduit 76 in accordance with the output signal from pressure transducer 262. The

, valve positioning servo 232 will serve to move valve 78 towards closure in response to an increase in pressure and to open the valve upon a decrease in pressure. Finally, as shown in FIG. 15m, signal E-S will pass through OR gate 264 and will actuate the over-rider electro-pneumatic relay 266 previously referred to, the purpose of this operation being to over-ride the integral unloader to cause the compressor 20 to operate fully loaded if required during the energy source cycle. As will be described below, the same operation will take place during the defrost cycle, during which an output signal D will be emitted as shown in FIG. 15m.

In FIG. 15b, a block diagram illustrates the automatic operating mechanism which may be used to convert the operation of the heat pump system of the present invention to the defrost cycle. As has previously been described, a temperature sensing element or thermostat (identified in FIG. 15b as T70) located on a metal surface of the air entering side of the source-sink exchanger 70 is provided to sense the presence of frost on exchanger 70. The output signal from the thermostat T70 is applied to a gate 268 shown in FIG. 15b. Every ninety minutes the gate 268 is enabled by an output from a timer 270 for a period of 15 seconds. When the gate 268 is enabled it will pass the signal from the thermostat T70 to a detector 272, which will set in response to an applied Signal from thermostat T70 indicating a temperature below a predetermined level. When the detector 272 sets it will, in turn, produce an output signal which will pass through a normally enabled gate 274. A signal passing through gate 274 is designated A and will identify the transformation of this system into the first stage of the defrost cycle. As will be seen in FIG. 15b, the production of signal A will simultaneously result in the production of a signal D.

The production of signal A as above described produces the following results: As shown in FIG. 15C, signal A will pass through OR gate 246 and be applied to the C input of valve operator 210 which will, in turn, close valve 62. Signal A will also pass through OR gate 248 (see FIG. 15d) and will pass through the O input of valve operator 214 which will open valve 34. Signal A will also pass through OR gate 250 (see FIG. 15e) and will be applied to the O input of valve operator 218 which then will open valve 112. As shown in FIG. 15j, signal A will be applied to a close signal generator 268, whose output signal will pass through OR gate 270 and will be applied to valve positioning servo 272. The latter in response to such signal will close valve 44. Reference to FIG. 15g will show that signal A will have the same function as to the operation described therein as does signal E-S during the energy source cycle; that is, it will pass through OR gate 252 to enable gate 254 and the opening of back pressure valve 52 will vary in accordance with the intensity of the output signal of pressure transducer 256. As shown in FIG. 15h, signal A will have the same effect therein as does signal E-S during the energy source cycle; that is, it will pass through OR gate 258 to enable gate 260 and the opening of valve 7 S will vary in accordance with the signal produced by pressure transducer 262.

As was mentioned previously, Whenever signal A is produced, signal D will also be produced. It Was also previously mentioned that the production of signal D will inhibit gates 204 and 266 (see FIG. l) so as to terminate operation of the system under the energy source and standard cycles. As will be seen in FIGS. 15j, i, j and m, signal D also has additional functions. As shown in FIG. 15f, the opening of valve 44 is responsive to an output signal from a thermostat in conduit 142. The output signal of such thermostat (identified in FIG. 15j as T14Z) will pass through a normally enabled gate 280, through OR gate 270 and will be applied to valve positioning servo 272, which adjusts the opening in valve 44 in accordance with the signal emitted by T142. As will be seen in FIG. 15f, gate 280 is inhibited by the production of signal D, and thus the operation of T142 will have no 1effect on the opening of valve 44 during the defrost cyc e.

As shown in FIG. 151', a source of power 282 is operative during normal operation of the heat pump system to run pump 156 by means of motor 286. On the production of output signal D, however, a switch 284 is opened disconnecting the power source 282 from the motor 286 and pump 156 rendered inoperative. Similarly, as will be shown in FIG. 15j, signal D acts to put heater 144 in operation. Finally, as shown lin FIG. 15m, signal D passes through OR gate 264 into over-rider 266 to cause compressor to operate under full load, or under reset controlof integral unloaders, as is the case during the energy source cycle.

With reference again to FIG. 15b, once signal A (the first stage of the defrost cycle) has begun to be produced due to the combined operations of the 90 minute timer 270 and T70, it will continue to be produced until the second stage of the defrost cycle comes into play. The latter will take place by virtue of the operation of a thermostat in low temperature fiuid circuit 126, which may be suitably placed in conduit 154. The output signal of this thermostat (indicated in FIG. 15b as T154) will pass through a gate 300 enabled by signal D to a detector 302 which will set in response to the signal applied from the thermostat T154, indicating that the temperature of the low temperature uid circulating in circuit 126 has reached a certain perdetermined level. When the detector 302 sets, it will in turn emit a signal B to start the second stage of the defrost cycle. At the same time, the signal B from detector 302 will inhibit gate 274, thus cutting off signal A.

Signal B will have the effect illustrated in FIGS. 15c- 15lz 15k and 1511. Thus, as shown in FIG. 15C, signal B will open valve 62 as did signal S previously described. As shown in FIG. 15d, signal B Will have the effect produced by signal S and will close valve 34. FIG. 15e also illustrates that signal B has the same effect as does signal S in closing valve 112. In FIG. 151, it wiil be seen that signal B is applied to an open signal generator 306, whose output signal will pass through OR gate 270 and will be applied to valve positioning servo 272 which will thereupon open valve 44. Similarly, as shown in FIG. 15g, signal B will open valve 52 after being applied to open signal generator 308, the signal of which will pass through OR gate 222 and will be applied to valve positioning servo 224 to open valve S2. In FIG. 15h, signal B will have the same effect as does signal S in closing valve 78. As shown in FIG. 15k, signal B will render inoperative pump 13S by opening a switch 310 which is normally closed. The switch 310 connects a source of power 312 to energize a motor 314, which drives the pump 138. Finally, as shown in FIG. 1511, signal B will have two functions with respect to dampers 120 and blowers 116. With respect to the former, signal B will be applied to a close signal generator 316, whose output signal will pass through OR gate 238 and be applied to positioning servo 240 which in response thereto will close dampers 120. At the same time, signal B will pass through OR gate 244 and will turn off blowers 116.

As will be seen by reference once again in FIG. 15b, signal D will also be produced simultaneously with the production of output signal B; thus, it will be produced throughout the defrost cycle. As a result of this fact, the same valves and other mechanisms which are affected by signal D during the production of signal A will also apply during the production of signal B.

When the thermostat on exchanger (T44) senses an increase in temperature of the outer surface of exchanger 70 to a predetermined level indicating the removal of frost from exchanger 70, its output signal will set detector 320 which, by its output signal, will in turn reset detectors 272 and 302, thus terminating the production of signal B as well as signal D. Since output signal D will no longer be produced at this point, gates 204 and 206 will correspondingly cease to be inhibited and operation of the system will once again be placed under control of T124 and thus be placed either on energy source or standard cycle as the case may be.

As will be apparent, an automatic control system such as has been described above with respect to the system illustrated in FIGURES 1-13 can also be suitably employed for the automatic operation of the system of FIG- URE 14. The modifications required for such adoption will be readily apparent to those skilled in the art.

As will further be apparent from the foregoing description, the novel heat pump system of the present invention may be used in a number of environments and for a variety of purposes. For example, while the primary application of the system Will be for industrial and commercial building air conditioning accomplished by passing air in heat exchange contact with the high and low temperature fluids produced in circuits 124 and 126, the high and low temperature fluids may be used as such. Similarly, the systern may be used to control energy input and outgo of commercial processes, including chemical processes and the like.

The heat pump system of the present invention provides numerous significant advantages. Quite obviously, one of the most significant advantages is the provision of a system capable of automatically performing a defrost function by means of a single outside combination coil while utilizing a non-reversing arrangement of refrigerant ow through the heat pump system. Another significant advantage is that the present system is capable of performing the above function while simultaneously producing high and low temperature fluid on a year-round basis, completely independent of normal source temperatures. As a result of the unique manner of effecting the above advantages, most of the components of the present system may be of a conventional type, permitting the obtaining of the significant advantages of the present invention Without significant re-design costs.

A further significant feature of the present invention which will be apparent from the foregoing description is that hot water is continually supplied to a point of use throughout each of the three cycles except for one brief interval (which probably extends over a period of only one minute out of each minutes) during the defrost cycle. A still further important feature of the present invention resides in the fact that, contrary to most conventional heat pumps on the market today, the heat for defrosting need not come from the building or process in connection with which the present system is being utilized.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. For example, while the source-sink exchanger and the other related elements of the heat pump have been illustrated in the drawings as being in close proximity to one another and compacted into a single unit, it is Within the present invention to physically separate one or more such elements from one another while maintaining a closed refrigerant circuit, i.e., to have the exchanger 70, blowers 116 and dampers 120, and various appropriate connections physically separated from the unit proper. Another illustration of a modification which may be made is the substitution of other varieties of mechanisms than the thermostat T70 to detect the presence of frost on exchanger 70 and to convert the system to the defrost cycle. For example, a switch Whose operation is sensitive to the pressure on the high side of the system (i.e., to the pressure in conduit 22 in FIGURE l) may be employed for the same purpose. This switchwould be keyed to the operation of a timing mechanism such as the timer 270 so that the defrost cycle could come into play only periodically, as was the case with thermostat T70. Similarly, a simple timing mechanism may be used to automatically switch the system into defrost cycle at fixed intervals. The relative advantages of such modifications to the preferred embodiment (thermostat T70) will be apparent to those skilled in the art. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning andrange of equivalency of the claims are therefore intended to be embraced therein.

What is claimed is:

1l. In a heat pump system comprising in series and with refrigerant circulating conduits connecting them in a closed Asystem a compressor, a first condenser, first expansion means and a first evaporator, the improvement comprising: a second condenser, second expansion means and a second evaporator; first means forestablishing refrigerant flow connections within said closed system between the high pressure side of said compressor, through said first and second condensers, and through said first expansion means; and second means for establishing7 refrigerant flow connections within said closed system between the downstream side of said first condenser, through said second expansion means, through said second evaporator and to the low pressure side of said compressor.

2. A heat pump system `as defined in claim i including means for rendering operative said first means while rendering inoperative said second means under a first set of conditions; and means for rendering operative said second means while rendering inoperative said first means under a second set of conditions.

y3. A heat pump system as defined in claim 2 including means associated with said second means for establishing a refrigerant fiow connection with said closed system between the `downstream side of said first condenserand through said first expansion means when said second means is rendered operative.

4. A heat pump system as defined in claim 3 including means for circulating a fiuid to be cooled in heat exchange relationship with said first evaporator and to a point of use for said fiuid; and means for cutting off circulation of said fiuid to said point of use while continuing circulation of said fiuid in heat exchange relationship with said first evaporator and in contact with heating means.

5. A `heat pump as defined in claim 4 including means for circulating fiuid to be heated in heat exchange relationship with said first condenser.

6. A heat pump as defined in claim '5 including means placing said second condenser and said second evaporator in heat exchange relationship to one another so that when the former expels heat at least a portion of said heat is transferred to the latter.

7. A heat pump as defined in claim `6 wherein said lastmentioned means comprises a common heat exchange surface between and in contact with said second condenser and said second evaporator.

t8. A heat pump as defined in claim 7 wherein said common heat exchange surface between said second condenser and `said second evaporator is provided by means of a series of fins, said second condenser and second evaporator being mounted on said fins in a tube and fin arrangement.

9. A heat pump as defined in cla-im 6 wherein means are provided to purge refrigerant from said second condenser and to transfer it to the flow connections leading to Isaid second evaporator under said second set of conditions.

. 10. In a heat pump system comprising in series and 1'8 with refrigerant circulating conduits connecting them in a closed system a compressor, a first condenser, first expansion means and first evaporator, the improvement comprising: a second condenser, second expansion means and a second evaporator; first means for establishing refrigerant flow connections within said closed system between the high pressure side of said compressor, throughI said first and second condensers and through said first expansion means; and second means for establishing refrigerant iiow connections within said closed system between said first condenser, through said second expansion means, through said second evaporator and to the low pressure side of said compressor; and means placing said second condenser and said second evaporator in heat exchange relationship to one another so that when the former expels heat at least a portion of said heat is transferred to the latter.

11. In a heat pump system comprising in series and with refrigerant circulating conduits connecting them in a closed system a compressor, a first condenser, first expansion means and a first evaporator, the improvement comprising: a second condenser, second expansion means and a second evaporator; first means responsive to a net energy excess in the system for establishing refrigerant fiow connnections within said closed system between the high pressure side of said compressor, through said first and second condensers, and through said first expansion means; second means responsive to an energy demand in the system for establishing refrigerant flow connections within said closed system between the downstream side of said first condenser, through said second expansion means, through said second evaporator and to the low pressure side of said compressor; means rendering said first means inoperative when said second means is operative; and means rendering said second means inoperative when said first means is operative.

12. A heat pump system as defined in claim 11 additionally including means placing said second condenser and second evaporator in heat exchange relationship to one another so that when the former expels heat at least a portion of said heat is transferred to the latter; third means responsive to a frost condition on said second evaporator for operating the heat pump system (1) during a first period by establishing refrigerant fiow between the high pressure side of said compressor, through said first condenser, through said second expansion means and said second evaporator, and back to the low pressure side of said compressor and (2) 'during a second period by establishing refrigerant flow in heat exchange relationship with a heated fiuid, through said compressor through said second condenser and back into said compressor.

` 13. A heat pump system as defined in claim 12 including means for passing a fiuid to be cooled in heat exchange relationship with refrigerant in said first ev-aporator; :said third means including means for heating said fluid 4tolbe cooled during said first period, the resulting heated fiuid being the heated fiuid with which said refrigerant is passed in heat exchange relationship during said second period.

14. In a heat pump cycle in which a fiuid refrigerant gas is compressed, condensed at a first point, evaporated at a second point and recompressed in a continuous cycle, a method of carrying out said cycle under varying energy demands of the system comprising:

(1) when there is a net energy demand in the system, causing said refrigerant to evaporate at least partially at a third point separated from said first and second points and passing a fiuid in heat exchange relationship with said evaporating refrigerant at said third point, thereby supplying heat to said refrigerant;

(2) when there is a net energy excess in the system, causing said refrigerant to condense at least partially at a fourth point separated from said first and second points and passing a fiuid in heat exchange relationship withv said condensing refrigerant at said fourth 19 point, thereby removing heat from said refrigerant.

15. A method as dened in claim 14 wherein said refrigerant is condensed at least partially and substantially continuously both under net energy demand and net energy excess conditions at said first point in heat exchange relationship with a fluid to be supplied to a point of use as a high temperature fluid; said refrigerant being evaporated at least partially and substantially continuously both under net energy demand and net energy excess conditions at said second point in heat exchange relationship with a fiuid to be supplied to a point of use as a low temperature fiuid.

16. A method as defined in claim 15 wherein said refrigerant is evaporated at said third point in an evaporator which periodically becomes coated with frost and wherein said evaporator is defrosted by:

(l) conducting the heat pump cycle during a first period by compressing said refrigerant gas; condensing said compressed refrigerant at said first point; evaporating said refrigerant at said third point; recompressing the resulting evaporated refrigerant; repeating the cycle in this manner for the duration of said first period; and heating said low temperature fiuid during said first period until the temperature of said low temperature fluid has reached a predetermined level; Y

(2) when said low temperature fiuid has reached said predetermined level, conducting the heat pump cycle during a second period by passing said refrigerant in heat exchange relationship to the low temperature uid which has been heated during said first period; compressing said refrigerant while in gaseous form; and causing said refrigerant to condense at least partially in heat exchange relationship with said frosted evaporator, the heat thereby given off serving to defrost said evaporator.

17. A method as defined in claim 16 wherein circulation of said high temperature fluid in heat exchange relationship with said refrigerant is suspended during said second period.

18. A method as defined in claim 16 wherein circulation of fluid in heat exchange relationship with said evaporating refrigerant at said third point is suspended during said second period.

19. A method as defined in claim 16 wherein the compressor used to compress said refrigerant is operated under full load during the net energy demand and defrosting stages of the heat pump cycle.

20. A method as defined in claim 16 wherein the predetermined temperature level to which said low temperature fiuid is heated is that temperature at which sufficient energy has been stored in said low temperature fiuid and associated mass to satisfy the defrost requirements during the second period of the defrosting operation.

21. A method as defined in claim 16 wherein each of said net energy demand, net energy excess and defrost operations of said heat pump cycle are carried out without reversal of flow of refrigerant.

22. In the operation of a heat pump system comprising a compressor, a condenser in heat exchange relationship with a fluid to be heated by condensation of refrigeration in said condenser; an outdoor evaporator; and an indoor evaporator in heat exchange relationship with a fiuid to be cooled, said system being a closed system with the compressor, condenser, outdoor evaporator and indoor evaporator being connected together by means of refrigerant flow conduits, a method of defrosting said outdoor evaporator when frost has formed thereon comprising the steps of (l) operating the heat pump system during a first period by compressing said refrigerant gas; condensing said compressed refrigerant in said condenser; evaporating said refrigerant in said outdoor evaporator; recompressing the resulting evaporated refrigerant; repeating the cycle in this manner for the duration CFI 20 of said first period; and heating said fluid to be cooled during said first period until the temperature of said fiuid to be cooled has reached a predetermined level;

(2) when said fluid to be cooled has reached said predetermined level, operating the heat pump system during a second period by passing said refrigerant in heat exchange relationship to the fluid to be cooled which has been heated during said first period; compressing said refrigerant while in gaseous form; and causing said refrigerant to condense at least partially in heat exchange relationship with said frosted outdoor evaporator, the heat thereby given off serving to defrost said outdoor evaporator.

23. A method as defined in claim 22 wherein circulation of said fluid to be heated in heat exchange relationship to the refrigerant in said condenser is suspended during said second period.

24. In a heat pump system comprising in series and with refrigerant circulating conduits connecting them in a closed system a compressor, a first condenser, first expansion means and a first evaporator, the improvement comprising: a second condenser, second expansion means and a second evaporator; first means for establishing refrigerant flow connections within said closed system between the high pressure side of said compressor, through said first and second condensers in series and through said first expansion means; and second means for establishing refrigerant flow connections within said closed system between the downstream side of said first condenser, through said second condenser, through said second expansion means, through said second evaporator and to the low pressure side of said compressor.

25. A heat pump system as defined in claim 24 wherein means are provided for passing a fiuid in heat exchange relationship with said second condenser and with said second evaporator and wherein said second condenser and said second evaporator are so arranged with respect to one another and with respect to said Huid-passing means that heat energy passing from said second condenser to said fluid is transmitted to said second evaporator by said fluid.

26. In a heat pump system comprising in series and with refrigerant circulating conduits connecting them in a closed system a compressor, a first condenser, first expansion means and a first evaporator, the improvement comprising: a second condenser, a third condenser, second expansion means and a second evaporator; first means responsive to a net energy excess in the system for establishing refrigerant flow connections within said closed system between the high pressure side of said compressor, through said first, second and third condensers, and through said rst expansion means; second means responsive to an energy demand in the system for establishing refrigerant fiow connections within said closed system between the downstream side Iof said first condenser, through said second expansion means, through said second evaporator and to the low pressure side of said compressor; means rendering said first means inoperative when said second means is operative; and means rendering said second means inoperative when said first means is operative.

27. In a heat pump system comprising in series and with refrigerant circulating conduits connecting them in a closed system a compressor, a first condenser, first expansion means and a first evaporator, the improvement comprising: a second condenser and a third condenser; and means responsive to a net energy excess in the system for establishing refrigerant flow connections within said closed system between the high pressure side of said compressor, through said first, second and third condensers, and through said first expansion means.

28. A system as defined in claim 27 including means for heating hot water by means of heat resulting from condensation of refrigerant in at least one `of said second and third condensers.

29. In a heat pump cycle in which a fiuid refrigerant gas is compressed, condensed, evaporated and recompressed in a continuous cycle, a method of supplying energy to the cycle comprising condensing said refrigerant gas in said continuous cycle by passing a fluid in heat exchange relationship with said refrigerant gas; causing said condensed refrigerant to evaporate at least partially at a point separated from the point at which said refrigerant is evaporated in said continuous cycle and passing a uid in heat exchange relationship with said evaporating refrigerant at said separated point, thereby supplying heat to said refrigerant, and simultaneously evaporating at least a portion of said refrigerant at said point in said continuous cycle while passing a fluid in heat exchange relationship with said last-mentioned evaporating refrigerant so as to make available simultaneously a source of low temperature upid to a point of use; maintaining said source of low temperature fluid distinct and separate from said fluid in heat exchange relationship with said evaporating refrigerant at said separated point after said fluids have passed out of heat exchange relationship with their respective evaporating refrigerants; and also maintaining said source of low temperature fluid distinct and separate from said fluid in heat exchange relationship with said refrigerant gas after said fluids have respectively passed out of heat exchange relationship with the evaporating refrigerant and refrigerant gas into which they are brought References Cited by the Examiner UNITED STATES PATENTS 1,643,179 9/ 1927 Sawyer 62-226 1,882,969 10/ 1932 Scherer 62--78 2,221,688 11/ 1940 Gibson 62--324 2,249,856 7/1941 Ruff 62-117 2,293,360 8/ 1942 Reilly 62-418 2,293,482 8/1942 Ambrose 62-159 2,458,560 1/ 1949 Buchanan 62--207 2,474,304 6/ 1949 Clancy 62-140 2,912,834 11/1959 Mann 62-419 WILLIAM J. WYE, Primary Examiner. ROBERT A. OLEARY, Examiner.

UNITED STATES vPATENT OFFICE CERTIFICATE 0F CORRECTION Patent No. 3,224,214 December 21, 1965 Grason T. Nickell et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4, line 13, for "mentioned" read mention column 8, line 35, for "of the use" read of use column 10, line 32, for "through" read though column 13, line 26, for "serzo" read servo column 16, line 1, for "(Tl4)" read (T70) column 19, line 61, for "refrigeration" read refrigerant column 21, line 15, for 'Hlupd" read fluid Signed and sealed this 6th day of December 1966.

(SEAL) Attest:

ERNEST W. SW'IDER EDWARD I. BRENNER Attesting Officer Commissioner of Patents 

29. IN A HEAT PUMP CYCLE IN WHICH A FLUID REFRIGERANT GAS IS COMPRESSED, CONDENSED, EVAPORATED AND RECOMPRESSED IN A CONTINUOUS CYCLE, A METHOD OF SUPPLYING ENERGY TO THE CYCLE COMPRISING CONDENSING SAID REFRIGERANT GAS IN SAID CONTINUOUS CYCLE BY PASSING A FLUID IN HEAT EXCHANGE RELATIONSHIP WITH SAID REFRIGERANT GAS; CAUSING SAID CONDENSED REFRIGERANT TO EVAPORATE AT LEAST PARTIALLY AT A POINT SEPARATED FROM THE POINT AT WHICH SAID REFRIGERANT IS EVAPORATED IN SAID CONTINUOUS CYCLE AND PASSING A FLUID IN HEAT EXCHANGE RELATIONSHIP WITH SAID EVAPORATING REFRIGERANT AT SAID SEPARATED POINT, THEREBY SUPPLYING HEAT TO SAID REFRIGERANT, AND SIMULTANEOUSLY EVAPORATING AT LEAST A PORTION OF SAID REFRIGERANT AT SAID POINT IN SAID CONTINUOUS CYCLE WHILE PASSING A FLUID IN HEAT EXCHANGER RELATIONSHIP WITH SAID LAST-MENTIONED EVAPORATING REFRIGERANT 